1. Technical Field
The present invention relates a display sheet, a display device, an electronic device, and a display sheet driving method.
2. Related Art
For example, an electrophoretic display utilizing electrophoresis of particles is known as one constituting an image display portion of electronic paper (e.g., Japanese Unexamined Patent Application Publication No. 2009-145873). The electrophoretic display has excellent flexibility and power saving ability and is particularly suitable as the image display portion of electronic paper.
Japanese Unexamined Patent Application Publication No. 2009-145873 discloses a display device having a first electrode (two or more pixel electrodes) and a second electrode (common electrode) that are disposed facing each other and two or more microcapsules provided therebetween. In each microcapsule, a dispersion liquid is enclosed in which two or more positively charged black particles (second particles) and two or more negatively charged white particles (first particles) are dispersed in a liquid phase dispersion medium. The display device of Japanese Unexamined Patent Application Publication No. 2009-145873 is structured so that a desired image is displayed on a display surface by causing a desired electric field to act on each microcapsule, and then selecting for every microcapsule either one state of a black color display state in which the black particles are unevenly present at the display surface side (second electrode side) and a white display state in which the white particles are unevenly present at the display surface side.
However, according to the display device of Japanese Unexamined Patent Application Publication No. 2009-145873, when, in order to switch an image displayed on the display surface from a first image to a second image, an electric field corresponding to the second image is caused to act on each microcapsule, afterimages resulting from the first image are displayed on the display surface with the second image.
It is considered that such a problem arises for the following reasons. For example, the description is given to one microcapsule. When switching the display state from the black display state to the white display state, the black particles are moved to the first electrode side from the second electrode side and the white particles are moved to the second electrode side from the first electrode side. In this case, since the white particles are in a dispersion state in the liquid phase dispersion medium, the white particles reach the second electrode side in a short period of time. Then, the white particles move to the second electrode while the black particles are still moving near the second electrode, resulting in the fact that some black particles are surrounded by two or more white particles, and then the black particles stay at the second electrode side as they are. Thus, particles that need to move to the first electrode side under normal circumstances stay at the second electrode side without moving, and the particles affect the display color, which is considered to be a cause of the generation of afterimages described above.